72 lines
1.7 KiB
JavaScript
72 lines
1.7 KiB
JavaScript
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var charToInteger = {};
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var integerToChar = {};
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'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
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.split('')
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.forEach(function (char, i) {
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charToInteger[char] = i;
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integerToChar[i] = char;
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});
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function decode(string) {
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var result = [];
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var shift = 0;
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var value = 0;
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for (var i = 0; i < string.length; i += 1) {
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var integer = charToInteger[string[i]];
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if (integer === undefined) {
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throw new Error('Invalid character (' + string[i] + ')');
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}
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var hasContinuationBit = integer & 32;
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integer &= 31;
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value += integer << shift;
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if (hasContinuationBit) {
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shift += 5;
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}
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else {
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var shouldNegate = value & 1;
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value >>>= 1;
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if (shouldNegate) {
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result.push(value === 0 ? -0x80000000 : -value);
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}
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else {
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result.push(value);
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}
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// reset
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value = shift = 0;
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}
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}
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return result;
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}
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function encode(value) {
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var result;
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if (typeof value === 'number') {
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result = encodeInteger(value);
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}
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else {
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result = '';
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for (var i = 0; i < value.length; i += 1) {
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result += encodeInteger(value[i]);
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}
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}
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return result;
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}
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function encodeInteger(num) {
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var result = '';
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if (num < 0) {
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num = (-num << 1) | 1;
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}
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else {
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num <<= 1;
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}
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do {
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var clamped = num & 31;
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num >>>= 5;
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if (num > 0) {
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clamped |= 32;
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}
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result += integerToChar[clamped];
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} while (num > 0);
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return result;
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}
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export { decode, encode };
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